1. Field of the Technology
The present invention relates generally to mobile communication devices, such as portable wireless e-mail devices operating over cellular telecommunications networks, and more particularly to a method of selecting a communication network over which to operate based on the availability of different communication services in the communication networks.
2. Description of the Related Art
A mobile communication device, such as a cellular mobile station, may be capable of making and receiving telephone calls and/or sending and receiving data over a wireless communication network. Before it is able to do this, the cellular mobile station selects and registers with one of a plurality of communication networks which are available within a given geographic coverage area. After registering with the selected network, the mobile station operates in an idle mode where it “camps-on” a particular wireless communication channel of the network to monitor for its calls or messages. “Network selection” is the particular process performed by the mobile station for selecting the one communication network over which to register and operate.
Cellular telephony operation and network selection schemes are documented in standards specifications that govern the behavior of cellular mobile stations and associated systems. One well-known cellular standard is the Global System for Mobile Communication (GSM) standard. GSM 03.22/European Technical Standards Institute (ETSI) TX 100 930, Technical Specification (TS) 23.122 from the 3rd Generation Partnership Project (3GPP), and other related standards specifications describe the many details of cellular operation and network selection. These documents describe how a mobile station behaves as it roams between various regions and countries to maintain communication network coverage, primarily for the purposes of providing continuous telephone service.
In such a network, a mobile station performs network selection by initially determining the signal strengths of each one of the available base stations in a given coverage area. Thereafter, it searches for these identified base stations within a preferred network list that is stored in memory. The mobile station then selects the base station with strongest signal that is listed in the preferred network list. There may be several preferred network lists, commonly referred to as preferred public land mobile network (PPLMN) lists, stored on the SIM card. For example, the PPLMN lists may include a home PPLMN list, a user-controlled PPLMN (U-PPLMN) list, and an operator-controlled PLMN (O-PPLMN) list.
The above-described network selection method is commonly referred to as an “automatic” network selection method. As an alternative to this automatic selection method, an end-user of the mobile station may be provided with the ability to manually select from a plurality of listed available networks which are visibly displayed on the mobile device. This conventional network selection method may be referred to as a “manual” network selection method.
Other portable devices, such as personal digital assistants (PDAs), laptop computers, and portable e-mail devices, are better known to provide for the organization and management of text, files, messages, and/or other data. However, mobile data communication services, such as wireless e-mail and Internet access services, are becoming more and more popular in connection with these devices. Mobile devices providing for combined capabilities (e.g. both voice and data communication) also exist and are becoming increasingly popular. In addition to operating in accordance with GSM for voice capabilities, these mobile devices may operate in accordance with well-known General Packet Radio Service (GPRS) standard. GPRS is a packet-based communication protocol for mobile devices that allows data to be sent and received across a mobile telephone network.
In order to operate fully as intended, these mobile devices must have the appropriate communication services supported and made available by the communication network that it is registered with. Ideally, all communication networks around the world should support and make available all the different types of communication services that a mobile device is capable of providing. In practice, however, some communication networks do not have or cannot make a particular communication service (e.g. a data communication service) available to a mobile device. This problem may be partially mitigated in a given coverage area as there may be several communication networks from which the mobile device may select.
Conventional network selection, however, does not take into consideration the availability of other services (e.g. data communication services) in its decision-making process. As a result, an inadequate communication network may be selected by the mobile device. For example, a mobile device may select a communication network that can provide an acceptable voice service but not a data service, even though another adequate and available network could provide both the voice and the data service. Such conventional operation is undesirable, especially for mobile devices that are primarily intended to provide the end-user with a data communication service (e.g. portable e-mail devices).
Accordingly, there is a resulting need for a method and apparatus for selecting a communication network that overcome the deficiencies of the prior art.